<p>Realizing fault-tolerant quantum computing relies on efficient quantum error correction. Bosonic cat-state qubits offer a highly promising, hardware-efficient approach by intrinsically suppressing bit-flip errors. However, fully unlocking their potential demands fast and high-fidelity quantum nondemolition (QND) measurements. Here, we propose a high-fidelity QND readout protocol for cat-state qubits in a Kerr-nonlinear resonator utilizing an effective longitudinal interaction. By deriving analytical expressions and performing numerical simulations, we demonstrate that longitudinal readout achieves faster signal-to-noise ratio (SNR) growth and shorter measurement times than conventional dispersive readout. Furthermore, we show that injecting squeezed input states can exponentially enhance the SNR, while time-dependent coupling further reduces the measurement time. This scheme provides a robust pathway toward rapid and nondestructive measurement of cat qubits in near-term quantum processors.</p>